I pulled the trigger a bit early, the subject needs a bit better/consistent
formatting. It should be:
serial: liteuart: Add support for earlycon
On Sat, May 15, 2021 at 05:45:18PM +0900, Stafford Horne wrote:
> Most litex boards using RISC-V soft cores us the sbi earlycon, however
> this is not available for non RISC-V litex SoC. This patch enables
> earlycon for liteuart which is available on all Litex SoC's making
> support for earycon debugging more widely available.
>
> Signed-off-by: Stafford Horne <shorne@xxxxxxxxx>
> Cc: Florent Kermarrec <florent@xxxxxxxxxxxxxxxx>
> Cc: Mateusz Holenko <mholenko@xxxxxxxxxxxx>
> Cc: Joel Stanley <joel@xxxxxxxxx>
> Cc: Gabriel L. Somlo <gsomlo@xxxxxxxxx>
> ---
> .../admin-guide/kernel-parameters.txt | 5 +++
> drivers/tty/serial/Kconfig | 1 +
> drivers/tty/serial/liteuart.c | 31 +++++++++++++++++++
> 3 files changed, 37 insertions(+)
>
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 04545725f187..2d4a43af8de2 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1084,6 +1084,11 @@
> the driver will use only 32-bit accessors to read/write
> the device registers.
>
> + liteuart,<addr>
> + Start an early console on a litex serial port at the
> + specified address. The serial port must already be
> + setup and configured. Options are not yet supported.
> +
> meson,<addr>
> Start an early, polled-mode console on a meson serial
> port at the specified address. The serial port must
> diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
> index 0c4cd4a348f4..9ceffe6ab6fd 100644
> --- a/drivers/tty/serial/Kconfig
> +++ b/drivers/tty/serial/Kconfig
> @@ -1531,6 +1531,7 @@ config SERIAL_LITEUART
> depends on OF || COMPILE_TEST
> depends on LITEX
> select SERIAL_CORE
> + select SERIAL_EARLYCON
> help
> This driver is for the FPGA-based LiteUART serial controller from LiteX
> SoC builder.
> diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c
> index 64842f3539e1..38c472487e68 100644
> --- a/drivers/tty/serial/liteuart.c
> +++ b/drivers/tty/serial/liteuart.c
> @@ -372,6 +372,37 @@ static int __init liteuart_console_init(void)
> console_initcall(liteuart_console_init);
> #endif /* CONFIG_SERIAL_LITEUART_CONSOLE */
>
> +#ifdef CONFIG_SERIAL_EARLYCON
> +static void early_liteuart_putc(struct uart_port *port, int c)
> +{
> + while (litex_read8(port->membase + OFF_TXFULL))
> + cpu_relax();
> +
> + litex_write8(port->membase + OFF_RXTX, c);
> +}
> +
> +static void early_liteuart_write(struct console *console, const char *s,
> + unsigned int count)
> +{
> + struct earlycon_device *device = console->data;
> + struct uart_port *port = &device->port;
> +
> + uart_console_write(port, s, count, early_liteuart_putc);
> +}
> +
> +static int __init early_liteuart_setup(struct earlycon_device *device,
> + const char *options)
> +{
> + if (!device->port.membase)
> + return -ENODEV;
> +
> + device->con->write = early_liteuart_write;
> + return 0;
> +}
> +
> +OF_EARLYCON_DECLARE(liteuart, "litex,liteuart", early_liteuart_setup);
> +#endif /* CONFIG_SERIAL_EARLYCON */
> +
> static int __init liteuart_init(void)
> {
> int res;
> --
> 2.31.1
>
